Virus Structure & Classification
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Transcript of Virus Structure & Classification
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Virus Structure & ClassificationVirus Structure & Classification
developed bydeveloped by
Hugh B. FackrellHugh B. Fackrell
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Lecture OutlineLecture Outline
Scope of virologyScope of virology NomenclatureNomenclature VirionVirion Virus genome Virus genome Virus symmetryVirus symmetry Virion structureVirion structure
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Scope of VirologyScope of Virology
In developed countries viral infections are In developed countries viral infections are the most common cause of acute disease the most common cause of acute disease that does not require hospitalizationthat does not require hospitalization
In developing countries viral infections are In developing countries viral infections are a common cause of mortality and disability a common cause of mortality and disability especially among infants and childrenespecially among infants and children
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Viruses as a health hazardViruses as a health hazard
Now antibiotics effectively Now antibiotics effectively control most bacterial control most bacterial
infectionsinfections
Viruses pose a relatively greater Viruses pose a relatively greater and less controlled threat to and less controlled threat to
human healthhuman health
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VirusVirus
obligate intracellular parasiteobligate intracellular parasite delivers its genome into host celldelivers its genome into host cell
– genome is either DNA or RNAgenome is either DNA or RNA genome transcribed and translated by host genome transcribed and translated by host
synethetic machinarysynethetic machinary
Viruses are NOT cellular
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VirusVirus
submicroscopic particlessubmicroscopic particles– smallpox a large virus is at the limit of smallpox a large virus is at the limit of
resolution of the light microscoperesolution of the light microscope– most require use of electrom microscopemost require use of electrom microscope
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Viruses Infect All Life FormsViruses Infect All Life Forms
Bacteria>> bacteriophageBacteria>> bacteriophage PlantsPlants FungiFungi InsectsInsects FishFish ReptilesReptiles BirdBird MammalsMammals
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Viral NomenclatureViral Nomenclature
viruse families end with -viruse families end with -viridaeviridae– eg poxviridae retroviridaeeg poxviridae retroviridae
Virus subfamilies -Virus subfamilies -virinaevirinae– alphaherpesvirinae herpes simplexalphaherpesvirinae herpes simplex– gammaherpesvirinae- epstein Barr virusgammaherpesvirinae- epstein Barr virus
Virus genera -Virus genera -virusvirus– enterovirus- polio virusenterovirus- polio virus– lyssavirus -rabies viruslyssavirus -rabies virus
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SiglumSiglum
An abbreviation derived from a few or An abbreviation derived from a few or intial lettersintial letters
– (plural (plural siglasigla))
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Virus SiglaVirus Sigla
RRespiratory espiratory EEnteric and nteric and OOrphan rphan VirusViruseses PaPapilloma, pilloma, PoPolyoma & lyoma & VaVacuolating agent cuolating agent
VirusViruseses HepaHepatocytes & tocytes & RNARNA genome genome
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Sigla (cont)Sigla (cont)
Parvovirus -smallParvovirus -small Adenovirus - gland eg adenoid tissueAdenovirus - gland eg adenoid tissue Herpes- creeping- nature of lesionsHerpes- creeping- nature of lesions Toga virus - cloaked with envelopeToga virus - cloaked with envelope Arena virus - sand like lesionArena virus - sand like lesion Corona virus- crown like peplomersCorona virus- crown like peplomers Bunya virus - Bunyamwera AfricaBunya virus - Bunyamwera Africa Calcivirus - cup likeCalcivirus - cup like
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Herpes zosterHerpes zoster
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VirionVirion
A fully assembled infectious virusA fully assembled infectious virus At least two componentsAt least two components GenomeGenome
– DNA or RNADNA or RNA
– Single stranded or double strandedSingle stranded or double stranded
– Sense or antisenseSense or antisense CapsidCapsid
– Protective protein coatProtective protein coat
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DNA VirusesDNA Viruses
Parvovirus Parvovirus ssDNA, sense or antisense, ssDNA, sense or antisense, linearlinear
HepadnaAvirusHepadnaAvirus dsDNA,linear dsDNA,linear Papovavirus Papovavirus dsDNA,circulardsDNA,circular Adenovirus Adenovirus dsDNA,lineardsDNA,linear Herpes virus Herpes virus dsDNA,lineardsDNA,linear Pox virus Pox virus dsDNA, lineardsDNA, linear
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RNA VirusesRNA Viruses
ssRNA, Sense strand ssRNA, Sense strand -picornavirus, -picornavirus, calicivirus, togavirus, coronaviruscalicivirus, togavirus, coronavirus
ssRNA, antisense strand ssRNA, antisense strand -bunyavirus, -bunyavirus, orthomyxovirus, arenavirus, filovirus, orthomyxovirus, arenavirus, filovirus, rhabdovirus,paramyxovirusrhabdovirus,paramyxovirus
RetrovirusRetrovirus ssRNA 2 copies ssRNA 2 copies ReovirusReovirus dsRNA, 10-12 segments dsRNA, 10-12 segments
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CapsidCapsid
Protein coat that protects the genomeProtein coat that protects the genome protection against nucleasesprotection against nucleases few structural proteinsfew structural proteins
Capsids Self Assemble
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Virion SymmetryVirion Symmetry
Cubical SymmetryCubical Symmetry– AdenovirusAdenovirus– picorrnaviruspicorrnavirus
Helical SymmetryHelical Symmetry– FilovirusFilovirus– RhadovirusRhadovirus
Complex SymmetryComplex Symmetry– poxviruspoxvirus– T4 bacteriophageT4 bacteriophage
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Helical SymmetryHelical Symmetry
Helical rigidHelical rigid– Rhabdovirus,-rabiesRhabdovirus,-rabies
Helical pleomorphic Helical pleomorphic – Paramxyovirus -parainfluenzaParamxyovirus -parainfluenza– ,measles & respiratory syncytical virus,measles & respiratory syncytical virus– Orthomxyovirus -influenzaOrthomxyovirus -influenza
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Helical SymmetryHelical Symmetry
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RhabdovirusRhabdovirus
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Cubic SymmetryCubic Symmetry
Icosahedral SymmetryIcosahedral Symmetry 20 equilateral triangles20 equilateral triangles 12 vertices12 vertices 532 symmetry532 symmetry
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Icoshedral StructureIcoshedral Structure
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Complex SymmetryComplex Symmetry
Very rigid, defined structuresVery rigid, defined structures may or may not have envelopemay or may not have envelope
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Complex SymmetryComplex Symmetry
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Polio VirusPolio Virus
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PeplomerPeplomer
Glycoprotein spikesGlycoprotein spikes on viral envelopeon viral envelope coded by viral genomecoded by viral genome coronavirus,orthomyxovirus, coronavirus,orthomyxovirus,
arenavirus,Rhabdovirus,paramyxovirusarenavirus,Rhabdovirus,paramyxovirus
Determine viral host range
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Viral EnvelopeViral Envelope
Some viruses are surrounded by an Some viruses are surrounded by an additional covering - viral envelopeadditional covering - viral envelope
derived from host cell membranesderived from host cell membranes contact virus proteins internallycontact virus proteins internally glycosylated proteins externallyglycosylated proteins externally
50% of animal viruses have an envelope